Lighting devices of the above mentioned kind are used in luminaires in principle of any indoors or outdoors type, but particularly luminaires for outdoor lighting applications. Flexibility in placement of luminaires is very much desired. For instance for outdoor lighting, city architects are bound to mount luminaires on a pole at a fixed position relative to the ground in order to obtain a desired or required light distribution at a target area. Thus, the possibility to set the light distribution is limited to choosing the position on a pole before fixing the luminaire in that position. This in turn results in a clutter of light poles which is not desirable. More flexibility in placement has already been gained by suspending the luminaires from a wire but this still disturbs the street view with a crisscross of wires.
US-2010/029694 A1 describes a lighting device comprising a reflective electroactive polymer which is activated by means of a voltage control arrangement with a spatially varying voltage distribution. Thereby the shape of the reflective surface of the electroactive polymer can be continuously adapted to the given requirements.
Such a lighting device provides for an increased adaptability to the requirements given. However, such a lighting device has the drawback of requiring continuous application of a voltage for as long as a desired or required light distribution at a target area needs to be provided. This in turn results in high energy consumption and a less robust lighting device.
The term “target area” as used herein is intended to encompass any outdoor or indoor surface needing illumination as well as any temporary or virtual area at which the light distribution, preferably the angular intensity distribution of the light, is measured as a part of setting up a lighting device according to the invention. As an example, target areas in connection with outdoor luminaires may be for example outdoor surfaces such as streets, lanes, cycle paths, pavements, footpaths and like infrastructural surfaces.
The term “optical element” as used herein is intended to encompass any optical element usable for altering the path of the light beams emitted by a light source. Particularly, however, the term optical element is intended to encompass any one or more of a light reflective element, a light refractive element, a light diffractive element and a combination thereof.
As used herein, the term “first state” refers to a state in which the material of the substrate of the optical component comprises a first static modulus and is capable of changing shape when subjected to an activating force. Likewise, the term “second state” as used herein refers to a state in which the material of the substrate of the optical component comprises a second elastic modulus and is dimensionally stable. The first and second states are furthermore defined by that the first static modulus is smaller than the second static modulus. It is noted, that the static modulus of a material is generally calculated as the ratio of strain to stress of the material under static conditions.